Assessment of Metals in Tissues of Marine-Associated Birds in South Florida

Seabirds – broadly defined as any bird species associated with the marine environment – are exposed to a wide range of environmental contaminants. Vectors of exposure to metal pollution include by external contact, inhalation, and most often ingestion of food and incidental seawater. Seabirds are often considered marine ecosystem bioindicators due to their high trophic position, relatively long lifespan, and wide geographic ranges. We examined the concentration of total mercury (THg), lead (Pb), and cadmium (Cd), in the kidney, liver, breast muscle, and feathers of seven species of juvenile and adult seabirds commonly found in South Florida: brown pelican Pelecanus occidentalis (n=16), northern gannet Morus bassanus (n=16), double-crested cormorant Phalacrocorax auritus (n=15), royal tern Thalasseus maximus (n=15), herring gull Larus argentatus (n=9), laughing gull Leucophaeus atricilla (n=15), and osprey Pandion halietus (n=15). Trace amounts of lead and cadmium were found in the subsample of birds tested, suggesting that the birds living in south Florida do not face a significant threat from those metals. Results of total mercury in 101 specimens ranged from 0 to 45.07 mg/kg (dry wt), 0.15 to 132.13 mg/kg (wet wt), 0.06 to 352.35 mg/kg (wet wt), and 0.06 to 23.43 mg/kg (wet wt) in feathers, liver, kidney, and breast muscle respectively. Individual birds found to have the highest levels of total mercury were collected from centers in Monroe County. Osprey showed the highest total mercury values overall. These findings suggest a potential link to the Everglades and runoff into the Florida Bay, thus possibly exposing birds who utilize the Florida Bay at a higher risk for mercury poisoning

Vertebrate Photography: Second Place

The adult Brown Pelican flew overhead after spending some time on what remains of an old bridge in the Florida Keys. The breeding plumage is identified by the rich brown color that goes from the nape down the neck.https://nsuworks.nova.edu/occ_shuttershark_2017/1001/thumbnail.jp

Fauna: Third Place

https://nsuworks.nova.edu/occ-shuttershark-2018/1007/thumbnail.jp

Preliminary Assessment of Total Mercury in Tissues of Marine Associated Avifauna in the South Florida Region

Background/Question/Methods Marine associated avifauna (seabirds) are exposed to wide ranges of environmental contaminants due to spending a large portion of their time in the aquatic environment. Vectors of exposure to metal pollution include external contact, by inhalation, and most generally by ingestion of food and incidental seawater. Seabirds are often considered marine ecosystem bioindicators due to their high trophic level, long lives, and wide geographic ranges. All seabirds are not equally vulnerable to contaminants due to their generalist diets accompanied with varying abilities to excrete, metabolize, or sequester xenobiotics (foreign chemical substances). We examined the concentration of metals in the kidney, liver, breast muscle, and feathers of seven species of adult seabirds commonly found in South Florida: brown pelican Pelecanus occidentalis (n=15), northern gannet Morus bassanus (n=15), double-crested cormorant Phalacrocorax auritus (n=15), royal tern Thalasseus maximus (n=18), osprey Pandion haliaetus (n=15), herring gull Larus argentatus (n=8), and laughing gull Leucophaeus atricilla (n=16). Specimens were collected from four wildlife rehabilitation centers after the bird has died due to trauma or illness; specimens were frozen at death at the respective centers and dissected in the lab. Total mercury analysis used a Direct Mercury analyzer (DMA-80). Results/Conclusions Mercury is a highly toxic nonessential heavy metal that is emitted into the atmosphere by both natural and anthropogenic sources. Total mercury concentrations are thought to be equivalent to methylated mercury in tissues of organisms. Preliminary results were highly variable between species, individuals, and tissue types. Total mercury in the breast muscle, kidney, liver, and feathers ranged from 0.559 to 9.57 µg/g (dry wt), 2.06 to 12.16 µg/g (dry wt), 2.18 to 42.67 µg/g (dry wt), and 1.57 to 11.93 µg/g (dry wt), respectively. In the liver and kidney, values of methylmercury between 20 and 30 µg/g (wet wt) are associated with morbidity and mortality effects in terrestrial bird species. In feathers, total mercury concentrations of 5 µg/g (dry wt) are similarly associated with sublethal systemic and reproductive problems. Royal terns had the highest total mercury in three tissues whereas both gull species had the lowest values in all tissues. Additionally, cormorants and royal tern feathers had total mercury levels above the 5 µg/g threshold. Further assessment will help confirm whether seabird species in South Florida face a significant threat from metal pollution. Variability in metal concentrations between species and tissue types will be discussed in conjunction with concurrent stable isotope analyses in the context of trophic relationships

Assessment of Metal Contamination in Seabirds of South Florida

Metal concentrations will be determined in the kidney, liver, breast muscle, and feathers of brown pelicans (Pelecanus occidentalis), royal terns (Thalasseus maximus), laughing gulls (Leucophaeus atricilla), herring gulls (Larus argentatus), northern gannets (Morus bassanus), and double-crested cormorants (Phalacrocorax auritus) collected from four wildlife rehabilitation centers in South Florida. Currently, results for total mercury concentrations in all tissue samples with the exception of feathers have been determined for 44 birds. The mean total mercury concentrations in muscle, kidney and liver ranged from 0.559 to 9.57 μg/g (dry wt.), 2.06 μg/g to 12.16 μg/g (dry wt.), and 2.18 to 42.67 μg/g (dry wt.), respectively. Ongoing research will provide metal concentrations by March 2016 for nickel, copper, lead, zinc, cadmium, vanadium and manganese. In the liver and kidney, values of methylmercury between 20 and 30 μg/g (dry wt.) are reported to cause morbidity and mortality effects in birds. According to the values so far, royal terns and cormorants on average have values of total mercury exceeding or within the reported range. Further assessment will help to confirm whether the seabirds of South Florida face a significant threat from metal pollution

Accumulation of the Toxic Metal Mercury in Multiple Tissues of Marine-Associated Birds from South Florida

One of the best studied global “hot spots” for ecological mercury (Hg) contamination is south Florida (USA), where elevated Hg concentrations in environmental media and regional wildlife were first described over thirty years ago. While Hg contamination has lessened in this region, it is still critical to monitor Hg uptake and potential risks in south Florida wildlife, especially in marine-associated birds, which are known to accumulate potentially toxic Hg levels. In this study, total Hg (THg) concentrations were measured in liver, kidney, muscle, and feathers of 101 individuals from seven species of south Florida birds: brown pelican Pelecanus occidentalis, double-crested cormorant Phalacrocorax auratus, herring gull Larus argentatus, laughing gull Leucophaeus atricilla, northern gannet Morus bassanus, royal tern Thalasseus maximus, and osprey Pandion halietus. A sizeable proportion of individuals (\u3e 40%) were found to contain THg concentrations in internal tissues that exceeded estimated toxicity thresholds for Hg-related effects. Certain species, especially osprey, were found to exhibit a higher rate of threshold exceedances than others and should continue to be monitored for Hg-related effects in future studies. Feather THg concentrations exhibited a lower rate of toxicity threshold exceedances (12%) and were not significantly correlated with those in internal tissues in most cases, suggesting that they may not be well suited for monitoring Hg exposure in these species unless sources of data variation can be better understood. The results of the present study contribute significantly to our understanding of trends in Hg accumulation and Hg-related health risks in south Florida marine-associated birds